/Engine/Plugins/Runtime/XRBase/Source/XRBase/Public/HeadMountedDisplayFunctionLibrary.h
AngularVelocityRadPerSec is a vector where direction is the axis of rotation and length is the speed of rotation in radians per second. Note that it is not difficult to rotate a controller at more than 0.5 or 1 rotation per second briefly and some mathmatical operations (such as conversion to quaternion) lose rotations beyond 180 degrees or 360 degrees. In some cases that is OK becuase the resulting final rotation is the same, but in some cases it would generate incorrect results.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, Category="Input|XRTracking", Meta=(DeprecatedFunction, DeprecationMessage="Use new GetControllerTransformForTime2 which represents angular velocity as an FRotator rather than in the non-standard way this function represented it.")) static bool GetControllerTransformForTime ( [UObject](API\Runtime\CoreUObject\UObject\UObject) * WorldContext, const int32 ControllerIndex, const [FName](API\Runtime\Core\UObject\FName) MotionSource, [FTimespan](API\Runtime\Core\Misc\FTimespan) Time, bool & bTimeWasUsed, FRotator & Orientation, FVector & Position, bool & bProvidedLinearVelocity, FVector & LinearVelocity, bool & bProvidedAngularVelocity, FVector & AngularVelocityAsAxisAndLength, bool & bProvidedLinearAcceleration, FVector & LinearAcceleration )